Direct smelting process and apparatus

ABSTRACT

A molten-bath based direct smelting process and apparatus for producing metals from a ferrous material is disclosed. The process includes injecting feed materials being solid material and carrier gas into a molten bath at a velocity of at least 40 m/s through at least one downwardly extending solids injection lance having a delivery tube of internal diameter of 40-200 mm that is located so that a central axis of an outlet end of the lance is at an angle of 20 to 90 degrees to a horizontal axis. The feed materials injection generates a superficial gas flow of at least 0.04 Nm 3 /s/m 2  within the molten bath at least in part by reactions of injected material in the bath. The gas now causes molten material to be projected upwardly as splashes, droplets and streams and form an expanded molten bath zone, with the gas flow and the upwardly projected molten material causing substantial movement of material within the molten bath and strong mixing of the molten bath. The feed materials are selected so that, in an overall sense, the reactions of the feed materials in the molten bath are endothermic. The process also includes injecting an oxygen-containing gas into an upper region of the vessel via at least one oxygen gas injection lance and post-combusting combustible gases released from the molten bath.

[0001] The present invention relates to a process and an apparatus forproducing molten metal (which term includes metal alloys), in particularalthough by no means exclusively iron, from ferrous material, such asores, partly reduced ores and metal-containing waste streams.

[0002] The present invention relates particularly to a molten metalbath-based direct smelting process and an apparatus for producing moltenmetal from a ferrous material.

[0003] One known molten bath-based direct smelting process for producingmolten ferrous metal is the DIOS process. The DIOS process includes apre-reduction stage and a smelt reduction stage. In the DIOS process ore(8 mm) is pre-heated (750° C.) and pre-reduced (10 to 30%) in fluidisedbeds using offgas from a smelt reduction vessel which contains a moltenbath of metal and slag, with the slag forming a deep layer on the metal.The fine (−3 mm) and coarse (−8 mm) components of the ore are separatedin the pre-reduction stage of the process. Coal and pre-heated andpre-reduced ore (via two feed lines) are fed continuously into the smeltreduction furnace from the top of the furnace. The ore dissolves andforms FeO in the deep layer of slag and the coal decomposes into charand volatile matter in the slag layer. Oxygen is blown through aspecially designed lance that improves secondary combustion in thefoamed slag. Oxygen jets burn carbon monoxide that is generated with thesmelting reduction reactions, thereby generating heat that istransferred to the molten slag. The FeO is reduced at the slag/metal andslag/char interfaces. Stirring gas introduced into the hot metal bathfrom the bottom of the smelt reduction vessel improves heat transferefficiency and increases the slag/metal interface for reduction. Slagand metal are tapped periodically.

[0004] Another known direct smelting process for producing moltenferrous metal is the AISI process. The AISI process also includes apre-reduction stage and a smelt reduction stage. In the AISI processpre-heated and partially pre-reduced iron ore pellets, coal or cokebreeze and fluxes are top charged into a pressurised smelt reactor whichcontains a molten bath of metal and slag. The coal devolatilises in theslag layer and the iron ore pellets dissolve in the slag and then arereduced by carbon (char) in the slag. The process conditions result inslag foaming. Carbon monoxide and hydrogen generated in the process arepost combusted in or just above the slag layer to provide the energyrequired for the endothermic reduction reactions. Oxygen is top blownthrough a central, water cooled lance and nitrogen is injected throughtuyeres at the bottom of the reactor to ensure sufficient stirring tofacilitate heat transfer of the post combustion energy to the bath. Theprocess offgas is de-dusted in a hot cyclone before being fed to a shafttype furnace for pre-heating and pre-reduction of the pellets to FeO orwustite.

[0005] Another known direct smelting process, which relies on a moltenmetal layer as a reaction medium, and is generally referred to as theHIsmelt process, is described in International applicationPCT/AU96/00197 (WO 96/31627) in the name of the applicant.

[0006] The HIsmelt process as described in the International applicationcomprises:

[0007] (a) forming a bath of molten metal and slag in a vessel;

[0008] (b) injecting into the bath:

[0009] (i) metalliferous feed material, typically metal oxides; and

[0010] (ii) a solid carbonaceous material, typically coal, which acts asa reductant of the metal oxides and a source of energy; and

[0011] (c) smelting the metalliferous feed material to metal in themetal layer.

[0012] The HIsmelt process also comprises injecting oxygen-containinggas into a space above the bath and post-combusting reaction gases, suchas CO and H₂, released from the bath and transferring the heat generatedto the bath to contribute to the thermal energy required to smelt themetalliferous feed materials.

[0013] The HIsmelt process also comprises forming a transition zone inthe space above the nominal quiescent surface of the bath in which thereis a favourable mass of ascending and thereafter descending droplets orsplashes or streams of molten materiel which provide an effective mediumto transfer to the bath the thermal energy generated by post-combustingreaction gases above the bath.

[0014] The HIsmelt process as described in the international applicationis characterised by forming the transition zone by injecting a carriergas, metalliferous feed material, and solid carbonaceous material intothe bath through a section of the side of the vessel that is in contactwith the bath and/or from above the bath so that the carrier gas and thesolid material penetrate the bath and cause molten material to beprojected into the space above the surface of the bath.

[0015] The HIsmelt process as described in the International applicationis an improvement over earlier forms of the HIsmelt process which formthe transition zone by bottom injection of gas and/or carbonaceousmaterial into the bath which causes droplets and splashes and streams ofmolten material to be projected from the bath.

[0016] The applicant has carried out extensive research and pilot plantwork on direct smelting processes and has made a series of significantfindings in relation to such processes.

[0017] In general terms, the present invention provides a directsmelting process for producing metals (which term includes metal alloys)from a ferrous material which includes the steps of:

[0018] (a) forming a bath of molten metal and molten slag in ametallurgical vessel;

[0019] (b) injecting feed materials being solid material and carrier gasinto the molten bath at a velocity of at least 40 m/s through adownwardly extending solids injection lance having a delivery tube ofinternal diameter of 40-200 mm that is located so that a central axis ofan outlet end of the lance is at an angle of 20 to 90 degrees to ahorizontal axis and generating a superficial gas flow of at least 0.04Nm³/s/m² within the molten bath (where m² relates to the area of ahorizontal cross-section through the molten bath) at least in part byreactions of injected material in the bath which causes molten materialto be projected upwardly as splashes, droplets and streams and form anexpanded molten bath zone, the gas flow and the upwardly projectedmolten material causing substantial movement of material within themolten bath and strong mixing of the molten bath, the feed materialsbeing selected so that, in an overall sense, the reactions of the feedmaterials in the molten bath are endothermic; and

[0020] (c) injecting an oxygen-containing gas into an upper region ofthe vessel via at least one oxygen gas injection lance andpost-combusting combustible gases released from the molten bath, wherebyascending and thereafter descending molten material in the expandedmolten bath zone facilitate heat transfer to the molten bath.

[0021] The expanded molten bath zone is characterised by a high volumefraction of gas voidages throughout the molten material.

[0022] Preferably the volume fraction of gas voidages is at least 30% byvolume of the expanded molten bath zone.

[0023] The splashes, droplets and streams of molten material aregenerated by the above-described flow of gas within the molten bath.Whilst the applicant does not wish to be bound by the followingcomments, the applicant believes that the splashes, droplets and streamsare generated by a churn-turbulent regime at lower gas flow rates and bya fountain regime at higher gas flow rates.

[0024] Preferably the gas flow and the upwardly projected moltenmaterial cause substantial movement of material into and from the moltenbath.

[0025] Preferably the solid material includes ferrous material and/orsolid carbonaceous material.

[0026] The above-described expanded molten bath zone is quite differentto the layer of foaming slag produced in the above-described AISIprocess.

[0027] Preferably step (b) includes injecting feed materials into themolten bath so that the feed materials penetrate a lower region of themolten bath.

[0028] Preferably the expanded molten bath zone forms on the lowerregion of the molten bath.

[0029] Preferably step (b) includes injecting feed materials into themolten bath via the lance at a velocity in the range of 80-100 m/s.

[0030] Preferably step (b) includes injecting feed materials into themolten bath via the lance at a mass flow rate of up to 2.0 t/m²/s wherem² relates to the cross-sectional area of the lance delivery tube.

[0031] Preferably step (b) includes injecting feed materials into themolten bath via the lance at a solids/gas ratio of 10-25 kg solids/Nm³gas.

[0032] More preferably the solid gas ratio is 10-18 kg solids/Nm³ gas.

[0033] Preferably the gas flow within the molten bath generated in step(b) is at least 0.04 Nm³/s/m² at the quiescent surface of the moltenbath.

[0034] More preferably the gas flow within the molten bath is at a flowrate of at least 0.2 Nm³/s/m².

[0035] More preferably the gas flow rate is at least 0.3 Nm³/s/m².

[0036] Preferably the gas flow rate is less than 2 Nm³/s/m².

[0037] The gas flow within the molten bath may be generated in part as aresult of bottom and/or side wall injection of a gas into the moltenbath, preferably the lower region of the molten bath.

[0038] Preferably the oxygen-containing gas is air or oxygen-enrichedair.

[0039] Preferably the process includes injecting air or oxygen-enrichedair into the vessel at a temperature of 800-1400° C. and at a velocityof 200-600 m/s via at least one oxygen gas injection lance and forcingthe expanded molten bath zone in the region of the lower end of thelance away from the lance and forming a “free” space around the lowerend of the lance that has a concentration of molten material that islower than the molten material concentration in the expanded molten bathzone; the lance being located so that: (i) a central axis of the lanceis at an angle of 20 to 90° relative to a horizontal axis; (ii) thelance extends into the vessel a distance that is at least the outerdiameter of the lower end of the lance; and (iii) the lower end of thelance is at least 3 times the outer diameter of the lower end of thelance above the quiescent surface of the molten bath.

[0040] Preferably the concentration of molten material in the free spacearound the lower end of the lance is 5% or less by volume of the space.

[0041] Preferably the free space around the lower end of the lance is asemi-spherical volume that has a diameter that is at least 2 times theouter diameter of the lower end of the lance.

[0042] Preferably the free space around the lower end of the lance is nomore than 4 times the outer diameter of the lower end of the lance.

[0043] Preferably at least 50%, more preferably at least 60%, by volumeof the oxygen in the air or oxygen enriched air is combusted in the freespace around the lower end of the lance.

[0044] Preferably the process includes injecting air or oxygen-enrichedair into the vessel in a swirling motion.

[0045] The term “smelting” is understood herein to mean thermalprocessing wherein chemical reactions that reduce the ferrous feedmaterial take place to produce liquid metal.

[0046] The term “quiescent surface” in the context of the molten bath isunderstood to mean the surface of the molten bath under processconditions in which there is no gas/solids injection and therefore nobath agitation.

[0047] Preferably the process includes maintaining a high slag inventoryin the vessel relative to the molten ferrous metal in the vessel.

[0048] The amount of slag in the vessel, ie the slag inventory, has adirect impact on the amount of slag that is in the expanded molten bathzone.

[0049] The relatively low heat transfer characteristics of slag comparedto metal is important in the context of minimising heat loss from theexpanded molten bath zone to the water cooled side walls and from thevessel via the side walls of the vessel.

[0050] By appropriate process control, slag in the expanded molten bathzone can form a layer or layers on the side walls that adds resistanceto heat loss from the side walls.

[0051] Therefore, by changing the slag inventory it is possible toincrease or decrease the amount of slag in the expanded molten bath zoneand on the side walls and therefore control the heat loss via the sidewalls of the vessel.

[0052] The slag may form a “wet” layer or a “dry” layer on the sidewalls. A “wet” layer comprises a frozen layer that adheres to the sidewalls, a semi-solid (mush) layer, and an outer liquid film. A “dry”layer is one in which substantially all of the slag is frozen.

[0053] The amount of slag in the vessel also provides a measure ofcontrol over the extent of post combustion.

[0054] Specifically, if the slag inventory is too low there will beincreased exposure of metal in the expanded molten bath zone andtherefore increased oxidation of metal and dissolved carbon in metal andthe potential for reduced post-combustion and consequential decreasedpost combustion, notwithstanding the positive effect that metal in theexpanded molten bath zone has on heat transfer to the metal layer.

[0055] In addition, if the slag inventory is too high the one or morethan one oxygen-containing gas injection lance/tuyere will be buried inthe expanded molten bath zone and this minimises movement of top spacereaction gases to the end of the or each lance/tuyere and, as aconsequence, reduces potential for post-combustion.

[0056] The amount of slag in the vessel, ie the slag inventory, may becontrolled by the tapping rates of metal and slag.

[0057] The production of slag in the vessel may be controlled by varyingthe feed rates of metalliferous feed material, carbonaceous material,and fluxes to the vessel and operating parameters such asoxygen-containing gas injection rates.

[0058] Preferably the process includes controlling the level ofdissolved carbon in molten iron to be at least 3 wt % and maintainingthe slag in a strongly reducing condition leading to FeO levels of lessthan 6 wt %, more preferably less than 5 wt %, in the slag.

[0059] Preferably ferrous material is smelted to metal at leastpredominantly in the lower region of the molten bath. Invariably, thisregion of the vessel is where there will be a high concentration ofmetal.

[0060] In practice, there will be a proportion of the ferrous materialthat is smelted to metal in other regions of the vessel. However, theobjective of the process of the present invention, and an importantdifference between the process and prior art processes, is to maximisesmelting of ferrous material in the lower region of the molten bath.

[0061] Step (b) of the process may include injecting feed materialsthrough a plurality of solids injection lances and generating the gasflow of at least 0/04 Nm³/s/m² within the molten bath.

[0062] The injection of ferrous material and carbonaceous material maybe through the same or separate lances.

[0063] Preferably the process includes causing molten material to beprojected above the expanded molten bath zone.

[0064] Preferably the level of post-combustion is at least 40%, wherepost-combustion is defined as:$\frac{\left\lbrack {CO}_{2} \right\rbrack + \left\lbrack {H_{2}O} \right\rbrack}{\left\lbrack {CO}_{2} \right\rbrack + \left\lbrack {H_{2}O} \right\rbrack + \lbrack{CO}\rbrack + \left\lbrack H_{2} \right\rbrack}$

[0065] where:

[0066] [CO₂]=volume % of CO₂ in off-gas

[0067] [H₂O]=volume % of H₂O in off-gas

[0068] [CO]=volume % of CO in off-gas

[0069] [H₂]=volume % of H₂ in off-gas

[0070] The expanded molten bath zone is important for 2 reasons.

[0071] Firstly, the ascending and thereafter descending molten materialis an effective means of transferring to the molten bath the heatgenerated by post-combustion of reaction gases.

[0072] Secondly, the molten material, and particularly the slag, in theexpanded molten bath zone is an effective means of minimising heat lossvia the side walls of the vessel.

[0073] An important difference between the preferred embodiment of theprocess of the present invention and prior art processes is that in thepreferred embodiment the main smelting region is the lower region of themolten bath and the main oxidation (ie heat generation) region is aboveand in an upper region of the expanded molten bath zone and theseregions are spatially well separated and heat transfer is via physicalmovement of molten metal and slag between the two regions.

[0074] According to the present invention there is also provided anapparatus for producing metal from a ferrous material by a directsmelting process, which apparatus includes a fixed non-tiltable vesselthat contains a molten bath of metal and slag and includes a lowerregion and an expanded molten bath zone above the lower region, theexpanded molten bath zone being formed by gas flow from the lower regionwhich carries molten material upwardly from the lower region, whichvessel includes:

[0075] (a) a hearth formed of refractory material having a base andsides in contact with the lower region of the molten bath;

[0076] (b) side walls extending upwardly from the sides of the hearthand being in contact with an upper region of the molten bath and the gascontinuous space, wherein the side walls that contact the gas continuousspace include water cooled panels and a layer of slag on the panels;

[0077] (c) at least one lance extending downwardly into the vessel andinjecting oxygen-containing gas into the vessel above the molten bath;

[0078] (d) at least one lance injecting feed materials being ferrousmaterial and/or carbonaceous material and carrier gas into the moltenbath at a velocity of at least 40 m/s, the lance being located so that acentral axis of an outlet end of the lance is angled downwardly at anangle of 20 to 90° to a horizontal axis, the lance having a deliverytube for injecting feed materials which has an internal diameter of40-200 mm; and

[0079] (e) a means for tapping molten metal and slag from the vessel.

[0080] Preferably the feed material injection lance is located so thatthe outlet end of the lance is 150-1500 mm above the nominal quiescentsurface of a metal layer of the molten bath.

[0081] Preferably the feed materials injection lance includes a centralcore tube through which to pass the solid particulate material; anannular cooling jacket surrounding the central core tube throughout asubstantial part of its length, which jacket defines an inner elongateannular water flow passage disposed about the core tube, an outerelongate annular water flow passage disposed about the inner water flowpassage, and an annular end passage interconnecting the inner and outerwater flow passages at a forward end of the cooling jacket; water inletmeans for inlet of water into the inner annular water flow passage ofthe jacket at a rear end region of the jacket; an water outlet means foroutlet of water from the outer annular water flow passage at the rearend region of the jacket, whereby to provide for flow of cooling waterforwardly along the inner elongate annular passage to the forward end ofthe jacket then through the end flow passage means and backwardlythrough the outer elongate annular water flow passage, wherein theannular end passage curves smoothly outwardly and backwardly from theinner elongate annular passage to the outer elongate annular passage andthe effective cross-sectional area for water flow through the endpassage is less than the cross-sectional flow areas of both the innerand outer elongate annular water flow passages.

[0082] The present invention is described further by way of example withreference to the accompanying drawings of which:

[0083]FIG. 1 is a vertical section illustrating in schematic form apreferred embodiment of the process and the apparatus of the presentinvention;

[0084]FIGS. 2A and 2B join on the line A-A to form a longitudinalcross-section through one of the solids injection lances shown in FIG.1;

[0085]FIG. 3 is an enlarged longitudinal cross-section through a rearend of the lance;

[0086]FIG. 4 is an enlarged cross-section through the forward end of thelance; and

[0087]FIG. 5 is a transverse cross-section on the line 5-5 in FIG. 4.

[0088] The following description is in the context of smelting iron oreto produce molten iron and it is understood that the present inventionis not limited to this application and is applicable to any suitableferrous ores and/or concentrates—including partially reduced metallicores and waste revert materials.

[0089] The direct smelting apparatus shown in FIG. 1 includes ametallurgical vessel denoted generally as 11. The vessel 11 has a hearththat incudes a base 12 and sides 13 formed from refractory bricks; sidewalls 14 which form a generally cylindrical barrel extending upwardlyfrom the sides 13 of the hearth and which includes an upper barrelsection formed from water cooled panels (not shown) and a lower barrelsection formed from water cooled panels (not shown) having an innerlining of refractory bricks; a roof 17; an outlet 18 for off-gases; aforehearth 19 for discharging molten metal continuously; and a tap-hole21 for discharging molten slag.

[0090] In use, under quiescent conditions, the vessel contains a moltenbath of iron and slag which includes a layer 22 of molten metal and alayer 23 of molten slag on the metal layer 22.

[0091] The term “metal layer” is understood herein to mean that regionof the bath that is predominantly metal.

[0092] The space above the nominal quiescent surface of the molten bathis hereinafter referred to as the “top space”.

[0093] The arrow marked by the numeral 24 indicates the position of thenominal quiescent surface of the metal layer 22 and the arrow marked bythe numeral 25 indicates the position of the nominal quiescent surfaceof the slag layer 23 (ie of the molten bath).

[0094] The term “quiescent surface” is understood to mean the surfacewhen there is no injection of gas and solids into the vessel.

[0095] The vessel is fitted with a downwardly extending hot airinjection lance 26 for delivering a hot air blast into an upper regionof the vessel and post-combusting reaction gases released from themolten bath. The lance 26 has an outer diameter D at a lower end of thelance. The lance 26 is located so that:

[0096] (i) a central axis of the lance 26 is at an angle of 20 to 90°relative to a horizontal axis (the lance 26 shown in FIG. 1 is at anangle of 90°);

[0097] (ii) the lance 26 extends into the vessel a distance that is atleast the outer diameter D of the lower end of the lance; and

[0098] (iii) the lower end of the lance 26 is at least 3 times the outerdiameter D of the lower end of the lance above the quiescent surface 25of the molten bath.

[0099] The vessel is also fitted with solids injection lances 27 (twoshown) extending downwardly and inwardly through the side walls 14 andinto the molten bath with outlet ends 82 of the lances 27 at an angle of20-70° to the horizontal for injecting iron ore, solid carbonaceousmaterial, and fluxes entrained in an oxygen-deficient carrier gas intothe molten bath. The position of the lances 27 is selected so that theiroutlet ends 82 are above the quiescent surface 24 of the metal layer 22.This position of the lances 27 reduces the risk of damage throughcontact with molten metal and also makes it possible to cool the lances27 by forced internal water cooling without significant risk of watercoming into contact with the molten metal in the vessel. Specifically,the position of the lances 27 is selected so that the outlet ends 82 arein the range of 150-1500 mm above the quiescent surface 24 of the metallayer 22. In this connection, it is noted that, whilst the lances 27 areshown in FIG. 1 as extending into the vessel, the outlet ends of thelances 27 may be flush with the side wall 14. The lances 27 aredescribed in more detail with reference to FIGS. 2-5.

[0100] In use, iron ore, solid carbonaceous material (typically coal),and fluxes (typically lime and magnesia) entrained in a carrier gas(typically N₂) are injected into the molten bath via the lances 27 at avelocity of at least 40 m/s, preferably 80-100 m/s. The momentum of thesolid material/carrier gas causes the solid material and gas topenetrate to a lower region of the molten bath. The coal isdevolatilised and thereby produces gas in the lower bath region. Carbonpartially dissolves into the metal and partially remains as solidcarbon. The iron ore is smelted to metal and the smelting reactiongenerates carbon monoxide gas. The gases transported into the lower bathregion and generated via devolatilisation and smelting producesignificant buoyancy uplift of molten metal, solid carbon, and slag(drawn into the lower bath region as a consequence ofsolid/gas/injection) from the lower bath region which generates anupward movement of splashes, droplets and streams of molten metal andslag, and these splashes, and droplets, and streams entrain slag as theymove through an upper region of the molten bath. The gas flow generatedby the above-described injection of carrier gas and bath reactions is atleast 0.04Nm³/s/m² of the quiescent surface of the molten bath (ie thesurface 25).

[0101] The buoyancy uplift of molten metal, solid carbon and slag causessubstantial agitation in the molten bath, with the result that themolten bath expands in volume and forms an expanded molten bath zone 28that has a surface indicated by the arrow 30. The extent of agitation issuch that there is substantial movement of molten material within themolten bath (including movement of molten material into and from thelower bath region) and strong mixing of the molten bath to the extentthat there is reasonably uniform temperature throughout the moltenbath—typically, 1450-1550° C. with a temperature variation of the orderof 30° in each region.

[0102] In addition, the upward gas flow projects some molten material(predominantly slag) beyond the expanded molten bath zone 28 and ontothe part of the upper barrel section of the side walls 14 that is abovethe expanded molten bath zone 28 and onto the roof 17.

[0103] In general terms, the expanded molten bath zone 28 is a liquidcontinuous volume, with gas bubbles therein.

[0104] In addition to the above, in use, hot air at a temperature of800-1400° C. is discharged at a velocity of 200-600 m/s via lance 26 andpenetrates the central region of the expanded molten bath zone 28 andcauses an essentially metal/slag free space 29 to form around the end ofthe lance 26.

[0105] The hot air blast via the lance 26 post-combusts reaction gasesCO and H₂ in the expanded molten bath zone 28 and in the free space 29around the end of the lance 26 and generates high temperatures of theorder of 2000° C. or higher in the gas space. The heat is transferred tothe ascending and descending splashes droplets, and streams, of moltenmaterial in the region of gas injection and the heat is then partiallytransferred throughout the molten bath.

[0106] The free space 29 is important to achieving high levels of postcombustion because it enables entrainment of gases in the space abovethe expanded molten bath zone 28 into the end region of the lance 26 andthereby increases exposure of available reaction gases to postcombustion.

[0107] The combined effect of the position of the lance 26, gas flowrate through the lance 26, and upward movement of splashes, droplets andstreams of molten material is to shape the expanded molten bath zone 28around the lower region of the lance 26. This shaped region provides apartial barrier to heat transfer by radiation to the side walls 14.

[0108] Moreover, the ascending and descending droplets, splashes andstreams of molten material is an effective means of transferring heatfrom the expanded molten bath zone 28 to the molten bath with the resultthat the temperature of the zone 28 in the region of the side walls 14is of the order of 1450° C.-1550° C.

[0109] The construction of the solids injection lances is illustrated inFIGS. 2 to 5.

[0110] As shown in these figures, each lance 27 comprises a central coretube 31 through which to deliver the solids material and an annularcooling jacket 32 surrounding the central core tube 31 throughout asubstantial part of its length. Central core tube 31 is formed ofcarbon/alloy steel tubing 33 throughout most of its length, but astainless steel section 34 at its forward end projects as a nozzle fromthe forward end of cooling jacket 32. The forward end part 34 of coretube 31 is connected to the carbon/alloy steel section 33 of the coretube through a short steel adaptor section 35 which is welded to thestainless steel section 34 and connected to the carbon/alloy steelsection through a screw thread 36.

[0111] Central core tube 31 is internally lined through to the forwardend part 34 with a thin ceramic lining 37 formed by a series of castceramic tubes. The rear end of the central core tube 31 is connectedthrough a coupling 38 to a T-piece 39 through which particulate solidsmaterial is delivered in a pressurised fluidising gas carrier, forexample nitrogen.

[0112] Annular cooling jacket 32 comprises a long hollow annularstructure 41 comprised of outer and inner tubes 42, 43 interconnected bya front end connector piece 44 and an elongate tubular structure 45which is disposed within the hollow annular structure 41 so as to dividethe interior of structure 41 into an inner elongate annular water flowpassage 46 and an outer elongate annular water flow passage 47. Elongatetubular structure 45 is formed by a long carbon steel tube 48 welded toa machined carbon steel forward end piece 49 which fits within the frontend connector 44 of the hollow tubular structure 41 to form an annularend flow passage 51 which interconnects the forward ends of the innerand outer water flow passages 46, 47.

[0113] The rear end of annular cooling jacket 32 is provided with awater inlet 52 through which the flow of cooling water can be directedinto the inner annular water flow passage 46 and a water outlet 53 fromwhich water is extracted from the outer annular passage 47 at the rearend of the lance. Accordingly, in use of the lance cooling water flowsforwardly down the lance through the inner annular water flow passage 46then outwardly and back around the forward annular end passage 51 intothe outer annular passage 47 through which it flows backwardly along thelance and out through the outlet 53. This ensures that the coolest wateris in heat transfer relationship with the incoming solids material toensure that this material does not melt or burn before it dischargesfrom the forward end of the lance and enables effective cooling of boththe solids material being injected through the central core of the lanceas well as effective cooling of the forward end and outer surfaces ofthe lance.

[0114] The outer surfaces of the tube 42 and front end piece 44 of thehollow annular structure 41 are machined with a regular pattern ofrectangular projecting bosses 54 each having an undercut or dove tailcross-section so that the bosses are of outwardly diverging formationand serve as keying formations for solidification of slag on the outersurfaces of the lance. Solidification of slag on to the lance assists inminimising the temperatures in the metal components of the lance. It hasbeen found in use that slag freezing on the forward or tip end of thelance serves as a base for formation of an extended pipe of solidmaterial serving as an extension of the lance which further protectsexposure of the metal components of the lance to the severe operatingconditions within the vessel.

[0115] It has been found that it is very important to cooling of the tipend of the lance to maintain a high water flow velocity around theannular end flow passage 51. In particular it is most desirable tomaintain a water flow velocity in this region of the order of 10 metersper second to obtain maximum heat transfer. In order to maximise thewater flow rate in this region, the effective cross-section for waterflow through passage 51 is significantly reduced below the effectivecross-section of both the inner annular water flow passage 46 and theouter water flow passage 47. Forward end piece 49 of the inner tubularstructure 45 is shaped and positioned so that water flowing from theforward end of inner annular passage 46 passes through an inwardlyreducing or tapered nozzle flow passage section 61 to minimise eddiesand losses before passing into the end flow passage 51. The end flowpassage 51 also reduces in effective flow area in the direction of waterflow so as to maintain the increased water flow velocity around the bendin the passage and back to the outer annular water flow passage 47. Inthis manner, it is possible to achieve the necessary high water flowrates in the tip region of the cooling jacket without excessive pressuredrops and the risk of blockages in other parts of the lance.

[0116] In order to maintain the appropriate cooling water velocityaround the tip end passage 51 and to minimise heat transferfluctuations, it is critically important to maintain a constantcontrolled spacing between the front end piece 49 tubular structure 45and the end piece 44 of the hollow annular structure 41. This presents aproblem due to differential thermal expansion and contraction in thecomponents of the lance. In particular, the outer tube part 42 of hollowannular structure 41 is exposed to much higher temperatures than theinner tube part 43 of that structure and the forward end of thatstructure therefore tends to roll forwardly in the manner indicated bythe dotted line 62 in FIG. 4. This produces a tendency for the gapbetween components 44, 49 defining the passage 51 to open when the lanceis exposed to the operating conditions within the smelting vessel.Conversely, the passage can tend to close if there is a drop intemperature during operation. In order to overcome this problem the rearend of the inner tube 43 of hollow annular structure 41 is supported ina sliding mounting 63 so that it can move axially relative to the outertube 42 of that structure, the rear end of inner tubular structure 45 isalso mounted in a sliding mounting 64 and is connected to the inner tube43 of structure 41 by a series of circumferentially spaced connectorcleats 65 so that the tubes 43 and 45 can move axially together. Inaddition, the end pieces 44, 49 of the hollow annular structure 41 andtubular structure 45 are positively interconnected by a series ofcircumferentially spaced dowels 70 to maintain the appropriate spacingunder both thermal expansion and contraction movements of the lancejacket.

[0117] The sliding mounting 64 for the inner end of tubular structure 45is provided by a ring 66 attached to a water flow manifold structure 68which defines the water inlet 52 and outlet 53 and is sealed by anO-ring seal 69. The sliding mounting 63 for the rear end of the innertube 43 of structure 41 is similarly provided by a ring flange 71fastened to the water manifold structure 68 and is sealed by an O-ringseal 72. An annular piston 73 is located within ring flange 71 andconnected by a screw thread connection 80 to the back end of the innertube 43 of structure 41 so as to close a water inlet manifold chamber 74which receives the incoming flow of cooling from inlet 52. Piston 73slides within hardened surfaces on ring flange 71 and is fitted withO-rings 81, 82. The sliding seal provided by piston 73 not only allowsmovements of the inner tube 43 due to differential thermal expansion ofstructure 41 but it also allows movement of tube 43 to accommodate anymovement of structure 41 generated by excessive water pressure in thecooling jacket. If for any reason the pressure of the cooling water flowbecomes excessive, the outer tube of structure 41 will be forcedoutwardly and piston 73 allows the inner tube to move accordingly torelieve the pressure build up. An interior space 75 between the piston73 and the ring flange 71 is vented through a vent hole 76 to allowmovement of the piston and escape of water leaking past the piston.

[0118] The rear part of annular cooling jacket 32 is provided with anouter stiffening pipe 83 part way down the lance and defining an annularcooling water passage 84, through which a separate flow of cooling wateris passed via a water inlet 85 and water outlet 86.

[0119] Typically cooling water will be passed through the cooling jacketat a flow rate of 100 m³/hr at a maximum operating pressure of 800 kPato produce water flow velocities of 10 meters/minute in the tip regionof the jacket. The inner and outer parts of the cooling jacket can besubjected to temperature differentials of the order of 200° C. and themovement of tubes 42 and 45 within the sliding mountings 63, 64 can beconsiderable during operation of the lance, but the effectivecross-sectional flow area of the end passage 51 is maintainedsubstantially constant throughout all operating conditions.

[0120] It is to be understood that this invention is in no way limitedto the details of the illustrated construction and that manymodifications and variations will fall within the spirit and scope ofthe invention.

[0121] In that regard it is noted that the oxygen gas injection lancecan be integral with and form part of the upper body of a solidsinjections lance.

The claims defining the invention are as follows:
 1. A direct smeltingprocess for producing metals (which term includes metal alloys) from aferrous material which includes the steps of: (a) forming a bath ofmolten metal and molten slag in a metallurgical vessel; (b) injectingfeed materials being solid material and carrier gas into the molten bathat a velocity of at least 40 m/s through a downwardly extending solidsinjection lance having a delivery tube of internal diameter of 40-200 mmthat is located so that a central axis of an outlet end of the lance isat an angle of 20 to 90 degrees to a horizontal axis and generating asuperficial gas flow of at least 0.04 Nm³/s/m² within the molten bath(where m² relates to the area of a horizontal cross-section through themolten bath) at least in part by reactions of injected material in thebath which causes molten material to be projected upwardly as splashes,droplets and streams and form an expanded molten bath zone, the gas flowand the upwardly projected molten material causing substantial movementof material within the molten bath and strong mixing of the molten bath,the feed materials being selected so that, in an overall sense, thereactions of the feed materials in the molten bath are endothermic; and(c) injecting an oxygen-containing gas into an upper region of thevessel via at least one oxygen gas injection lance and post-combustingcombustible gases released from the molten bath, whereby ascending andthereafter descending molten material in the expanded molten bath zonefacilitate heat transfer to the molten bath.
 2. The process defined inclaim 1 wherein step (b) includes injecting feed materials into themolten bath so that the feed materials penetrate a lower region of themolten bath.
 3. The process defined in claim 1 or claim 2 wherein step(b) includes injecting feed materials into the molten bath via the lanceat a velocity in the range of 80-100 m/s.
 4. The process defined inclaim 3 wherein step (b) includes injecting feed materials into themolten bath via the lance at a mass flow rate of up to 2.0 t/m²/s wherem² relates to the cross-sectional area of the lance delivery tube. 5.The process defined in any one of the preceding claims wherein step (b)includes injecting feed materials into the molten bath via the lance ata solids/gas ratio of 10-25 kg solids/Nm³ gas.
 6. The process defined inclaim 5 wherein the solids/gas ratio is 10-18 kg solids/Nm³ gas.
 7. Theprocess defined in any one of the preceding claims wherein step (b)includes injecting feed materials through a plurality of solidsinjection lances and generating the gas flow of at least 0.04 Nm³/s/m²within the molten bath.
 8. The process defined in any one of thepreceding claims wherein the gas flow within the molten bath generatedin step (b) is at least 0.04Nm³/s/m² at the nominal quiescent surface ofthe molten bath.
 9. The process defined in claim 8 wherein the gas flowwithin the molten bath is at a flow rate of at least 0.2 Nm³/s/m². 10.The process defined in claim 9 wherein the gas flow rate is at least 0.3Nm³/s/m².
 11. The process defined in any one of the preceding claimswherein the gas flow within the molten bath generated in step (b) isless than 2 Nm³/s/m².
 12. The process defined in any one of thepreceding claims wherein the oxygen-containing gas injected into themolten bath in step (c) is air or oxygen-enriched air.
 13. The processdefined in claim 12 wherein step (c) includes injecting the air oroxygen-enriched air into the vessel at a temperature of 800-1400° C. andat a velocity of 200-600 m/s via at least one oxygen gas injection lanceand forcing the expanded molten bath zone in the region of the lower endof the lance away from the lance and forming a “free” space around thelower end of the lance that has a concentration of molten material thatis lower than the molten material concentration in the expanded moltenbath zone; the lance being located so that: (i) a central axis of thelance is at an angle of 20 to 90° relative to a horizontal axis; (ii)the lance extends into the vessel a distance that is at least the outerdiameter of the lower end of the lance; and (iii) the lower end of thelance is at least 3 times the outer diameter of the lower end of thelance above the quiescent surface of the molten bath.
 14. The processdefined in any one of the preceding claims wherein step (c) includesinjecting oxygen-containing gas into the vessel in a swirling motion.15. The process defined in any one of the preceding claims includescontrolling the level of dissolved carbon in molten iron to be at least3 wt % and maintaining the slag in a strongly reducing condition leadingto FeO levels of less than 6 wt %, more preferably less than 5 wt %, inthe slag.
 16. The process defined in any one of the preceding claimsincludes causing molten material to be projected into a top space abovethe expanded molten bath zone.
 17. The process defined in any one of thepreceding claims wherein step (c) includes post-combusting combustiblegasses so that the level of post-combustion is at least 40%, wherepost-combustion is defined as:$\frac{\left\lbrack {CO}_{2} \right\rbrack + \left\lbrack {H_{2}O} \right\rbrack}{\left\lbrack {CO}_{2} \right\rbrack + \left\lbrack {H_{2}O} \right\rbrack + \lbrack{CO}\rbrack + \left\lbrack H_{2} \right\rbrack}$

where: [CO₂]=volume % of CO₂ in off-gas [H₂O]=volume % of H₂O in off-gas[CO]=volume % of CO in off-gas [H₂]=volume % of H₂ in off-gas
 18. Anapparatus for producing metal from a ferrous material by a directsmelting process, which apparatus includes a fixed non-tiltable vesselthat contains a molten bath of metal and slag and includes a lowerregion and an expanded molten bath zone above the lower region, theexpanded molten bath zone being formed by gas flow from the lower regionwhich carries molten material upwardly from the lower region, whichvessel includes: (a) a hearth formed of refractory material having abase and sides in contact with the lower region of the molten bath; (b)side walls extending upwardly from the sides of the hearth and being incontact with an upper region of the molten bath and the gas continuousspace, wherein the side walls that contact the gas continuous spaceinclude water cooled panels and a layer of slag on the panels; (c) atleast one lance extending downwardly into the vessel and injectingoxygen-containing gas into the vessel above the molten bath; (d) atleast one lance injecting feed materials being ferrous material and/orcarbonaceous material and carrier gas into the molten bath at a velocityof at least 40 m/s, the lance being located so that a central axis of anoutlet end of the lance is angled downwardly at an angle of 20 to 90° toa horizontal axis, the lance having a delivery tube for injecting feedmaterials which has an internal diameter of 40-200 mm; and (e) a meansfor tapping molten metal and slag from the vessel.
 19. The apparatusdefined in claim 18 wherein the feed materials injection lance islocated so that the outlet end of the lance is 150-1500 mm above thenominal quiescent surface of a metal layer of the molten bath.